Modified pyrolysis systems for converting olefins to diolefins



United States Patent ()fifice 3,366,793 Patented Jan. 30, 1968 3,366,703 MGDIFHED PYROLYSIS SYSTEMS FOR CON- VERTING OLEFHNS T DIOLEFINS Kenneth 3. Fresh, Kent, Ohio, assignor to The Goodyear Tire & Rubber Company, Akron, Ohio, a corporation of Ohio No Drawing. Filed May 19, 1965, Ser. No. 457,225

The portion of the term of the patent subsequent to May 31, 1983, has been disclaimed 17 Claims. (Cl. 260-680) This invention relates generally to the pyrolysis of olefins. More specifically it relates to methods of improving the efficiency in the pyrolyzation of olefins. More specifically it relates to methods of improving the efliciency of the pyrolysis of certain specific olefins to form specific diolefins.

It is known that most olefins may be thermally decomposed by pyrolysis by subjecting them to relatively high temperatures. The terms cracking, decomposing, cracked, decomposed, pyrolysis, pyrolyzing and the like terms, as employed throughout this application and claims, is meant-that the olefin molecule splits into two or more fragments from the application of heat. These fragments which are thus formed by the application of heat themselves become molecules of other lower molecular weight materials. This will be explained in greater detail later in the specification.

This thermal pyrolysis process employed to decompose olefins into two or more lower molecular weight materials is to be distinguished from dehydrogenation processes which require the effect of a surface catalyst or at least stoichiometric quantities of a homogeneous dehydrogenation agent rather than heat alone to remove hydrogen from hydrocarbons to form more unsaturated hydrocarbons.

Usually the thermal decomposition or pyrolysis of olefins is conducted in a closed zone orreactor at temperatures usually ranging from about 300 C. to about 1000 C. The pyrolysis of olefins is usually conducted in the absence of oxygen or air. Olefins normally are pyrolyzed while they are in a gaseous state and may be pyrolyzed either relatively pure or as mixtures with other hydrocarbons, usually in mixture with a saturated hydrocarbon, i.e. a mixed feed stream of pentene and pentane or they may be in mixture with diluents such as nitrogen, steam and the like.

Pyrolysis of olefins usually results in the formation of two or-more lower molecular weight materials as indicated above. The particular lower molecular weight materials formed when olefins are pyrolyzed depends largely upon the configuration of the olefin subjected to the pyrolysis process. By the term configuration as used throughout this application and claims is'meant the position or location of the double bonds and the position or location of the side groups, if any, of the olefin in question. To explain this in more detail, an olefin containing 6 carbon atoms with a side chain such as a methyl group attached to the second carbon atom of the main or straight chain portion and the double bond in the 2 position, such a material is Z-methylpentene-Z, when subjected to pyrolysis, will upon decomposition produce as the predominant product the diolefin, isoprene or Z-methyl butadiene- 1,3, and a lower molecular weight parafiin, methane. On the other hand, a 6 carbon olefin having a methyl group attached to the second carbon atom of the straight chain and the double bond in the 1 position, such a compound is Z-methyl pentene-l, when pyrolyzed, will produce as the predominant product two other lower molecular weight olefins, isobutylene and ethylene. Therefore, the configuration of the particular olefin pyrolyzed usually designates the main or predominant products which result from the pyrolysis of the olefin. These differences in product obtained upon pyrolysis of olefinic isomers referred to above are due to the fact that olefins crack at the position beta to the double bond, that is, the scission of the olefin occurs at the carbon-to-carbon single bond that is in a position beta to the double bond or that the split'in the olefin occurs between two carbons that are first and second removed from the last carbon which has the double bond attached to it. Thus, to sum up, if olefins are to crack appreciably by the application of a moderate amount of heat, they must contain in their make-up a carbon-to-carbon single bond which is positioned beta to the carbon-to-carbon double bond. Therefore, wherever the term cracking of olefins, olefins cracked, olefins pyrolyzed or the like are employed in this application, is meant olefins which will crack upon the application of heat to usually form two lower molecular weight olefins or one lower molecular weight diolefin and a lower molecular weight saturate.

Employing favorable conditions conducive to pyrolysis of olefins, by application of heat, to form lower molecular weight materials, it has been found that olefins decompose at a very low rate per pass through the cracking zone. The'conditions found conducive to the cracking of olefins are the temperature, the residence time in the zone, the ratio of the olefin to the diluent, if any, employed. It is usually the practice, to effect an increase in the overall yield of such a process, to separate the unreacted or undecomposed olefin from the products resulting from the decomposition of a portion of the olefin and return or recycle the unreacted olefin to the cracking zone. It has been found, however, in thermal pyrolysis of olefins, regardless of how many recycles are employed, the ultimate yield orthe ultimate decomposition of the olefin to the desired roducts is not significantly greater than about 50 mole percent of the olefin being decomposed at moderate conversion pass levels. The remaining 50 mole percent of the starting olefin is usually converted to undesirable or unwanted products as a result of side reactions caused by the repeated exposure to high temperature, the long residence time and the recycling steps employed in the cracking process. Thereby, a fairly high percent of the starting material is, in a sense, wasted, in that, a portion of the starting material is converted to undesired products.

Therefore, this invention has as its main object a method whereby the overall yield of the desired, roducts produced by pyrolysis of an olefin may be increased. Another object is to provide a method whereby the yield per pass of desired products obtained when olefins are cracked may be increased. Another object is to increase the ultimate yield or the ultimate decomposition of olefins to the desired products. Still another object is to provide a method whereby the residence time in the cracking or pyrolysis zone of olefins may be decreased. Another object is to provide a method whereby olefins may be cracked at lower cracking temperatures. Another object is to provide a method whereby the formation of undesired products produced by side reactions during the pyrolysis of olefins may be decreased. Another object is to provide a method whereby the size of the equip ment necessary to crack a given volume of an olefin is reduced. Another object is to reduce the amount of material required to be recycled. Still another object is to provide a method to promote the pyrolysis of olefins to the desired products.

Accordingly, the present invention is a process whereby at least one olefin which contains in its molecule a carbon-to-carbon single bond in a position beta to the double bond is pyrolyzed with the aid of a mixture of at least one pyrolysis promoter and at least one pyrolysis initiator.

Materials which will aid in the pyrolysis of such olefin may be classified into two groups; one such group has been termed, in this application, initiators. The term initiator is meant to denote a material which, when subjected to the pyrolysis conditions usually employed in the pyrolysis of olefins, will themselves decompose to form one or more free radicals, usually an alkyl free radical. The term alkyl free radical is meant to denote a material such as a lower alkyl hydrocarbon which is deficient in a hydrogen. Examples of such free radicals being methyl radicals, ethyl radicals, propyl radicals, butyl radicals and the like. Representative examples of materials classified as initiators for the purpose of this invention which, under the pyrolysis conditions, will form such free radicals, are: acetaldehyde, ethylene oxide, azomethane, methylethyl ether, ethyl ether, acetone, methylethyl ketone, propionaldehyde and the like. Thus, the term initiator includes low molecular weight aldehydes, ethers and ketones. Other materials known to the art as initiators may also be used.

The other material which will aid in the pyrolysis of the olefins of this invention are termed promoters. Representative examples of suitable promoters are hydrogen sulfide; methyl mercaptan; hydrogen bromide; bromine; sulfur; bromine-containing compounds such as bromobenzene; bromotoluene; allyl bromide; alkyl bromides such as methylene bromide; ethyl bromide; alkyl mercaptans containing from two up to twelve carbon atoms, such as isopropyl mercaptan, butyl mercaptan, ethyl mercaptan and the like; dichloro methane; the reaction product resulting from one mole of hydrogen sulfide and at least one and not more than two moles of an amine, examples of which are ammonium hydrosulfide, ammonium sulfide and ammonium polysulfide containing from two to six sulfur atoms; aromatic hydrocarbons, examples of which are benzene, toluene and xylene and refractory olefins such as 2,3-dimethyl butene- 2, 2-methylbutene-2, isobutylene, butene-2 and propylene.

As is indicated above, the aid to pyrolysis of olefins of this invention is a mixture of the initiators and the promoters. Likewise, mixtures of initiators may be employed with a single promoter and a single initiator may be employed with a mixture of promoters or a mixture of a mixture of initiators and a mixture of promoters may be employed.

The promoter may be added to the pyrolysis mixture in various ways. One convenient method is to dissolve the mixture of promoters and initiators employed in the reactants, i.e. the olefin to be cracked or the water which is to be used to produce the steam used as a diluent. The pyrolysis aids may also be added separately to the cracking furnace or they may be added as a mixture.

The amount of pyrolysis aids employed in this invention has not been found to be too critical. Of course, a sufiicient amount should be employed to obtain a benefit and for economy purposes, large excesses should be avoided. Generally, about one mole percent of each of the pyrolysis initiator and the pyrolysis promoter has shown some benefit. Generally, it is desirable to employ about two mole percent to about seven mole percent of each of the components comprising the pyrolysis aid mixture. The ratio between the promoter and the initiator has not been found to be too critical and may vary from about 0.5/1 to about 20/1. Usually, no further benefit is obtained if about 50 mole percent of the combined pyrolysis aid is employed. (All of the mole percentages calculations are based on the total mole of olefins to be pyrolyzed.)

Generally, the pyrolysis of olefins in accordance with the practice of this invention may be carried out in any conventional manner usually employed in the art of olefin pyrolysis. Generally these conditions employed may be widely varied and are not critical. They usually depend upon the particular olefin to be cracked or pyrolyzed and the particular products which are desired. For instance, the cracking temperature may be varied widely from about 300 C. to about 1000 C. However, it is preferred to practice this invention at temperatures ranging between about 500 C. and about 900 C. and it is more preferable to employ temperatures ranging from about 600 C. to 800 C. The time that the olefins are in the cracking zone during the practice of this invention may range broadly from about 0.001 to about 3.0 seconds. However, depending upon the particular olefin cracked, the pyrolysis temperature and the products desired, this time may vary from about 0.05 to about 1.0 second and its is most preferred that this time range from about 0.1 to about 0.5 second. These times are referred to usually as residence time, that is residence time within the cracking zone and are defined as the time required for one molecule of incoming gas, whether it be reactant, diluent or both, to pass through the cracking zone. The cracking zone may be defined as the zone at which the temperature is elevated to the cracking or pyrolysis temperatures as indicated above.

Generally, the olefins which are cracked in accordance with this invention may be in pure form or in mixture with other hydrocarbons. The olefins to be cracked may also be mixed with an inert diluent. it is usually desirable to employ an inert diluent when cracking olefins in accordance with this invention. The term inert diluent is defined as a material which does not react with the olefin or interfere with the olefin pyrolysis process. Likewise, the diluent does not react with the desired products produced by the cracking at the cracking conditions employed or with the aid to pyrolysis materials employed, for instance, the pyrolysis promoters and initiators. Furthermore, this diluent likewise does not crack or decompose itself at the conditions employed. Examples of diluents suitable for use in this invention are steam, carbon dioxide, hydrogen, the inert gases such as helium, neon and argon or such parafiinic hydrocarbons as methane, ethane, or other hydrocarbons which themselves will not crack at the temperatures employed in the cracking conditions of this invention. The ratio of diluent t0 olefin to be cracked which may be employed in the practice of this invention, if any be employed, may Widely vary from about 0.5/1 to about 15 or more moles of diluent per mole of olefin. However, if more than about 15/ 1 ratio is employed, the improvement gained does not offset the cost accrued and the process could become uneconomical. Therefore, it is usually preferred to use a ratio of from about 2/ 1 or 3/1 to 4/ 1 in this invention. The diluent usually preferred in this invention is steam because of the ease of separation from the products of the pyrolysis.

The pressure employed in the cracking zone is not critical and may vary from about 10 millimeters of mercury to about 500 pounds per square inch gauge. However, it is preferred to employ pressures ranging from about 1 atmosphere to about pounds per square inch gauge in the practice of this invention. Generally, it is preferred to employ oxygen-free conditions when practicing this invention.

As was stated above, this invention is directed to methods of improving or increasing the efiiciency of the process of pyrolyzing olefins which may be the subject of a thermal pyrolysis process generally. Thus, olefins which, when subjected to the practice of this invention will split at the carbon-to-carbon single bond which is in the position beta to the double bond. It is most desirable to employ the process of this invention with those olefins which have a carbon-to-carbon single bond in a position beta to the double bond and which have the proper configuration so that when they decompose they result in products which predominantly form diolelrns.

Representative among the olefins having a carbon-to carbon single bond which is in a position beta to the double bond which will decompose to form predominantly butadiene-l,3 when cracked in the presence of at least one of the combination pyrolysis aids of this invention, are hexene-Z; 3-methyl pentene-l; pentene-2; cyclohexene; 3-methyl butene-l; Z-heptene; 3-methyl hexene-l; 5- methyl hexene-Z; 2-octene; S-methyl heptene-Z; 6-methyl heptene-2 and nonene-2.

Representative among the olefins having a carbon-tocarbon sin le bond which is in a position beta to the double bond which will decompose to form predominantly Z-methyl butadiene-1,3 or isoprene when cracked in the presence of at least one of the combination pyrolysis aids of this invention, are Z-methyl pentene-2; 3-methyl pentene-Z; 2-ethyl butene-l; 3,3-dimethyl butene-l; 2,3-dimethyl bntene-l; 2-methyl hexene-Z; 3-methyl hexene-2; 2,3-dimethyl pentene-l; 3,3-dimethyl pentene-l; Z-methyl hepiene-Z; 3-methyl heptene-Z; 3,3-dimethyl hexene-l; 3,5-dimethyl hexene-Z; Z-methyl octene-Z; 3-methyl octene-2; 3,3-dimethyl heptene-l; 2,5-dimethyl heptene-Z; 2,6-dimethyl heptene-Z and 2,5,5-trimethyl hexene-2.

Representative among the olefins having a carbon-tocarbon single bond which is in a position beta to the double bond which will decompose to form predominantly 2-ethyl butadiene-1,3 when cracked in the presence of at least one of the combination pyrolysis aids of this invention are 3-ethyl pentene-Z; 3-methyl hexene-3; and 3- ethyl hexene-Z.

Representative among the olefins having a carbon-tocarbon single bond which is in a position beta to the double bond which will decompose to form predominantly 2,3-dimethyl -butadiene-1,3 when cracked in the presence of at least one of the combination pyrolysis aids of this invention are 2,3-dimethyl pentene-2; 2,3,3-trimethyl butene-l; 2,3,3-trimethyl pentene-l; and 2,3-dimethyl heptene-Z.

Representative among the olefins having a carbon-tocarbon single bond which is in a position beta to the double bond which will decompose to form predominantly 3-methyl pentadiene-1,3 when cracked in the presence of at least one of the combination pyrolysis aids of this invention are: 3-methyl heptene-3 and 3,4-dimethyl hexene-2.

Representative among the olefins having a carbon-tocarbon single bond which is in a position beta to the double bond which will decompose to form predominantly Z-methyl pentadiene-l,3 and 4-methyl pentadiene-1,3 when cracked in the presence of at least one of the combination pyrolysis aids of this invention are: 2,4-dimethyl pentene-Z; 2-meth-yl heptene-B; 2-methyl-3-ethyl pentene-l and 2,6-dimethyl heptene-3.

Representative among the elefins having a carbon-tocarbon single bond which is in a position beta to the double bond which will decompose to form predominantly piperylenes when cracked in the presence of at least one of the combination pyrolysis aids of this invention are: hexene-3; 4-methyl pentene-Z; 4-methyl hexene-Z; 4- methyl heptene-Z; 3-ethyl hexene-l; 4,5-dimethyl heptene- 2; and 4,5,5-trimethyl hexene-Z.

As is stated above, it is most desirable to employ, in the process of this invention, those olefins which have in their molecular makeup the proper configuration so that when they do decompose, in accordance with the invention, they produce a predominance of diolefins. This invention, however, is also applicable to the cracking of other olefins which have in their molecular makeup configurations which upon decomposition, in accordance with the invention, produce a predominance of other olefins.

Representative of such olefins which will decompose to form ethylene, for instance, as the major product are pentene-l and Z-rnethylpentene-l.

Representative of the olefins which will decompose to form propylene as a major product are: hexene-l; 4- methylpentene-l; 4-methylhexene-l; S-methylhexene-l; 4- methylheptene-l; and S-methylheptene-l.

Representative of the olefins which will decompose to form isobutylene as a major product are: 2-methylpentene-l; Z-methylhexene-l; 2,4-dimethylpentene-l; and 4,4-dimethylpentene-l.

Representative of the olefins which will decompose to form butene-l and/or butene-Z as major products are: Z-methylheptene-l; and 2,4-dimethylhexene-l.

Representative of the olefins which will decompose to form Z-methylbutene-l and/or 3-methylbutene-1 and/or 2-methylbutene-2 as major products are: 6-methylheptene- 1; 4,4-dimethylhexene-l; 4,5-dirnethylhexene-1; and 2,6- dimethylheptene-l Of all of these olefins, it is particularly desired to produce isoprene by the practice of this invention by pyrolyzing Z-methylpentene-Z, 3-methylpentene-2, 2-ethylbutene- 1,2,3dimethylbutene-1 and 3,3-dimethylbutene-l.

The practice of this invention is illustrated by reference to certain ofthe following experiments which are intended to be representative rather than restrictive of the scope of this invention.

All of the experiments were performed in a cracking assembly consisting of a hairpin coil prepared from inch OD. 316 stainless steel tubing. This cracking coil was immersed in a bed of fluidized heat transfer powder. This heat transfer powder was a microspheroidal aluminasilica material normally employed as a cracking catalyst. This heat transfer powder was heated both by an electrical resistance heater and by combusting a natural gas flame directly in the fluidized powder bed. The temperature gradient from the top to the bottom of the bed was never more than about 5 to 6 C. and the gradient from the fluidized bed to the cracking zone was never more than about 5 to 6 C. The temperatures were measured within the fluidized bed by means of conventional thermocouple techniques. The cracking coil had conventional thermocouple wells and the temperature within the cracking zone was also measured by conventional thermocouple techniques. The procedure employed was to bring the heat transfer powder up to about 500 C. by employing the electrical resistance heaters, at the same time fluidizing the bed by means of air. Then a direct natural gas/air flame was employed to bring the heat transfer bed up to the desired cracking or operating temperature. The natural gas flame and products of the combustion and additional air was used to fluidize the powdered bed. The combination pyrolysis aid, promoter and initiator materials were mixed with the olefin, which was to be cracked, in the desired mole percentage prior to the olefin being passed through the cracking zone. Water and the olefin containing the pyrolysis aids, if any, were pumped at the proper rates necessary to produce the desired steam to hydrocarbon ratios and at an overall rate to give the desired residence time of the materials in the cracking zone. When all variables had been adjusted to give the desired operating conditions, the products of the cracking were collected; if liquid, by means of cooled receivers, and if gas, they were metered at atmospheric pressure and room temperature conditions. The products collected were analyzed for content and yields by conventional analytical methods. Conventional recycle techniques were employed to obtain the ultimate. yields and are reported as ultimate reaction efiiciencies. The per pass yields are reported as the yield per pass.

The results of each of the experiments as well as the operating conditions are reported in the table below,

wherein column 1 is to the experiment number, column 2 is the residence time, column 3 is the temperature employed in the pyrolysis, column 4 is the promoter and/ or initiator in mole percent, if any, based on the hydrocarbon pyrolyzed, column 5 is the initiator and/or promoter in mole percent, if any, on the hydrocarbon pyrolyzed, column 6 is the yield per pass of isoprene in mole percent and column 7 is the reaction efliciency in percent of the desired product, isoprene, per mole of olefin cracked employing conventional recycle techniques.

In experiment 1 no promoter or no initiator was employed and is considered a true thermal pyrolysis of 3- methyl-Z-pentene. In experiment 2 only an initiator was employed. In experiment 3 only a promoter was employed. Experiment 4 illustrates the practice of this invention ernploying the combination pyrolysis aid which is a mixture of both initiator and promoter. Experiment 5 is again considered a control since neither a promoter or an initiator was employed. In each of the experiments the products obtained from the pyrolysis of Z-methyl-Z-pentene was isoprene and methane.

between about 500 C. and about 900 C. for periods of time varying between about 0.001 to about 3.0 seconds to cleave the carbon-to-carbon single bond which is in a position beta to the double bond of said olefin in said mixture.

4. A process comprising providing a mixture of (l) at least one olefin selected from the group of Z-rnethylpentene-Z, 3-methylpentene-2, Z-ethylbutene l, 2,3-dimet-hylbutene-l and 3,3-dimethylbutene-1 and (2) a mixture of (A) at least one pyrolysis pr moter and (B) at TABLE I.PYROLYSIS OF 3-METHYL-2-PENTENE Residence l Isoprene Reaction Experiment No. Time, Temp, Promoter, Mole Initiator, Mole per- Yield, Eli'iciency,

Seconds 0. percent on 11C cent on HC Mole percent percent 0.15 663. 5 None Nonc. 15. 6 61. 2 0.15 673.0 o Aoetaldehyde 10% 20. 4 61.1 0. 678. 0 (NH4)2 S 8%.." None 25. 1 63.5 0.15 677. 0 (NHnzS 8%.. Acetaldehyde 10 28. 2 61. l 0.15 672. 4 None None 16. 9 61. 7

It can be seen from the table above that the practice of this invention gives improved results over the individual components alone. Similar such improvements can be obtained using other olefins, mixtures of other promoters and other initiators and employing various other pyrolysis conditions, each of which have been taught elsewhere in the specification.

While certain representative embodiments and details have been shOWn for the purpose of illustrating this inventi0r1, it will be apparent to those skilled in the art that various changes and modifications may be made therein without departing from the spirit or scope of the invention.

What is claimed is:

1. An olefin cracking process which comprises providing a mixture of (l) at least one olefin having in its molecule a carbon-to-carbon single bond which is in a position beta to the double bond and (2) a pyrolysis aid comprising a mixture of (A) at least one pyrolysis promoter and (B) at least one pyrolysis initiator, subsequently heating this mixture to cleave the carbon-tocarbon single bond which is in a position beta to the double bond of said olefin in said mixture.

2. An olefin cracking process which comprises providing a mixture of (l) at least one olefin having in its molecule a carbonto-carbon single bond which is in a position beta to the double bond and (2) a pyrolysis aid comprising a mixture of (A) at least one pyrolysis promoter and (B) at least one pyrolysis initiator, subsequently heating the mixture to elevated temperatures ranging from about 500 C. to about 900 C. for a time varying from about 0.001 to about 3.0 seconds to cleave the carbon-to'carbon single bond which is in a position beta to the double bond of said olefin in said mixture.

3. An olefin cracking process which comprises providing a mixture of (l) at least one olefin having in its molecule a canbon-to-carbon single bond which is in a position beta to the double bond and (2) a pyrolysis aid comprising a mixture of (A) at least one pyrolysis initiator selected from the group consisting of acetaldehyde, ethylene oxide, azomethane, methylethyl ether, ethyl ether, acetone, .methylethyl ketone and propionaldehyde, and (B) at least one cracking promoter selected from the group of hydrogen sulfide, methyl mercaptan, hydrogen bromide, bromine, allyl bromide, sulfur, bromobenzene, bromotoluene, methylene bromide, ethyl bromide, dichloromethane, ethyl mercaptan, propyl mercaptan, butyl mercaptan, benzene, toluene, xylene, 2,3-dimethylbutene- 2, 2-methylbutene-2, isobutylene, butene-Z, propylene and. the reaction product of one mole of hydrogen sulfide and at least one and not more than two moles of an amine, subsequently heating the mixture to temperatures ranging least one pyrolysis initiator, subsequently heating this mixture to cleave the carbon-tocarbon single bond which is in a position beta to the double bond of said olefin in said mixture.

5. A process comprising providing a mixture of (1) at least one olefin selected from the group consisting of Z-methylpentene-Z, 3-methylpentene-2, ZeThyIbutene-l, 2,3-dirnethylbntene-l and 3,3dimethylbutene-l and (2) a mixture of (A) at least one pyrolysis initiator selected from the group consisting of acetaldehyde, ethylene oxide, azomethane, met-hylethyl ether, ethyl ether, acetone, methylethyl ketone and proprionaldehydc and (B) at least one cracking promoter selected from the group consisting of hydrogen sulfide, methyl mercaptan, hydrogen bromide, bromine, allyl bromide, sulfur, bromobenzene, bromotoluene, methylene br mide, ethyl bromide, dichloromethane, ethyl mercaptan, propyl mercaptan butyl mercaptan, benzene, xylene, toluene, 2,3 dimethylbutene-Z, 2-methylbutene-2, isobutylene, butene-Z, propylene and the reaction product of one mole of hydrogen sulfide and at least one and not more than two moles of an amine, subsequently heating the mixture to temperatures ranging between about 500 C. and about 900 C. for periods of time varying between about 0.001 to about 3.0 seconds to cleave the carbon-to-carbon single bond which is in the position beta to the double bond of said olefin in said mixture.

6. The method according to claim 2 in which the mixture is comprised of acetaldehyde and hydrogen sulfide.

7. The method according to claim 2 in which the miX- ture is comprise-d of hydrogen sulfide and ethylene oxide.

8. The method according to claim 2 in which the mixture is comprised of acetaldehyde and hydrogen bromide.

9. The method according to claim 2 in which the mixture is comprised of ethylene oxide and hydrogen bromide.

10. The method according to claim 2 in which the mixture comprises acetaldehyde and the reaction product resulting from one mole of hydrogen sulfide and at least one and not more than two moles of an amine.

11. The method according to claim 2 in which the mixture comprises ethylene oxide and the reaction product resulting from one mole of hydrogen sulfide and at least one and not more than two moles of an amine.

12. The method according to claim 5 in which the mixture is comprised of acetaldehyde and hydrogen sulfide.

13. The method according to claim 5 in which the mixture is comprised of hydrogen sulfide and ethylene oxide.

14. The method according to claim 5 in which the mixture is com-prised of acetaldehyde and hydrogen bromide.

15'. The method according to claim 5 in which the mixture is comprised of ethylene oxide and hydrogen bromide.

16. The method according to claim 5 in which the mixture comprises acetaldehyde and the reaction product resulting from one mole of hydrogen sulfide and at least one and not more than two moles of an amine.

17. The method according to claim 5 in which the mixture comprises ethylene oxide and the reaction product resulting from one mole of hydrogen sulfide and at least one and not more than two moles of an amine.

References Cited UNITED STATES PATENTS 2,259,630 10/1941 Frey et a1. 260-683 5 3,209,048 9/1965 Burk et a1 260-680 3,211,737 10/1965 Burk et a1. 260-680 3,238,270 3/1966 Turnquest 260-680 3,254,136 5/1966 Frech 260-680 DELBERT E. GANTZ, Primary Examiner. 10 G. E. SCH-MITKONS, Assistant Examiner. 

1. AN OLEFIN CRACKING PROCESS WHICH COMPRISES PROVIDING A MIXTURE OF (1) AT LEAST ONE OLEFIN HAVING IN ITS MOLECULE A CARBON-TO-CARBON SINGLE BOND WHICH IS IN A POSITION BETA TO THE DOUBLE BOND AND (2) A PYROLYSIS AID COMPRISING A MIXTURE OF (A) AT LEAST ONE PYROLYSIS PROMOTER AND (B) AT LEAST ONE PYROLYSIS INITIATOR, SUBSEQUENTLY HEATING THIS MIXTURE TO CLEAVE THE CARBON-TOCARBON SINGLE BOND WHICH IS IN A POSITION BETA TO THE DOUBLE BOND OF SAID OLEFIN IN SAID MIXTURE. 